Molecular Dynamics Simulations of Nucleation of Lead Halide Perovskites

Paramvir Ahlawat^a, Michele Parrinello^b^,^c, Ursula Rothlisberger^a

^aLaboratory of Computational Chemistry and Biochemistry, Dept. of Chemistry, Ecole Polytechnique Fédérale de Lausanne, 4107, Lausanne, 1015, Switzerland

^bETH Zürich, Department of Chemistry and Applied Biosciences, Switzerland, Switzerland

^cUniversità della Svizzera italiana (USI), Lugano

Materials for Sustainable Development Conference (MATSUS)
Proceedings of nanoGe Fall Meeting19 (NFM19)

#PERFuDe19. Halide perovskites: when theory meets experiment from fundamentals to devices

Berlin, Germany, 2019 November 3rd - 8th

Organizers: Claudine Katan, Wolfgang Tress and Simone Meloni

Oral, Paramvir Ahlawat, presentation 251
DOI: https://doi.org/10.29363/nanoge.nfm.2019.251
Publication date: 18th July 2019

Control over morphology is essential to manufacture high efficiency and high stability perovskite solar cells (PSCs). Nucleation regulate the morphological evolution. Therefore, it is utterly important to get the atomic level details into the nucleation process of these materials. For this, experimental techniques are mostly limited by temporal and spatial resolution. In our alternate approach, we perform molecular dynamics (MD) simulations of nucleation of lead halide perovskites[1]. However, nucleation is a rare event and MD simulation suffer from unaffordable time scales. Multi-component nature of our system adds an extra level of difficulty. To overcome this, we employ enhanced sampling technique of metadynamics which explore the free energy surface based on collective variables (CVs). In this study, we design experimentally measured quantities as CVs and succesfully observe the formation of perovskite crystals in our simulations[1]. To shed light, we depict the molecular details of different stages involved in formation of perovskite crystals and find that monovalent cations initiate and control the nucleation. Our simulations also reveal the atomic level structural details of intermediate phases[2] during crystallization. We argue the role of these intermediates in stability and efficiency of PSCs and show the effects of temperatures on free energy profile of these structures. Based on our insights, we demonstrate new experiments to better control the morphology via: spin coating and homogeneous nucleation. In the end, we discuss our compelling efforts and insights on simulating nucleation of highly complex mixed-cations systems on TiO₂[3].

References:

[1] Ahlawat, P., Piaggi, P., Graetzel, M., Parrinello, M., & Rothlisberger, U. (2018). Atomistic Mechanism of the Nucleation of Methylammonium Lead Iodide Perovskite from Solution. arXiv preprint arXiv:1810.00759v2

[2] P. Ahlawat at el., in preparation

[3] P. Ahlawat at el. in preparation

References:

[1] Ahlawat, P., Piaggi, P., Grätzel, M., Parrinello, M., & Röthlisberger, U. (2018). Atomistic Mechanism of the Nucleation of Methylammonium Lead Iodide Perovskite from Solution. arXiv preprint arXiv:1810.00759v2

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